Sheets in Proteins

 A β-pleated sheet contains multiple peptide strands that are positioned adjacent to one another as the one shown on the right. ( (Initial scene) ) The planes of the pleats are formed by the planes of the peptide bond. The alpha carbons of the peptide chain are at the valleys and peaks of the pleats. The peptides are rainbow colored (blue amino end changing to red carboxy end) to show that the adjacent peptides are running in opposite directions making the sheet antiparallel. Another way of detecting the antiparallel sheet is by displaying as cartoon. The adjacent chains align so that hydrogne bonds are formed between the imino hydrogens of one chain and the carbonyl oxygens of an adjacent chain. These hydrogen bonds provide the major attractive force which maintains the sheet structure. Psi and phi values that permit this alignment in antiparallel sheets have median values of +1350 and -1390, respectively. The median values for a parallel sheet are +1130 and -1190.

Twisted sheets are found in globular proteins. Unlike the above two types of sheets the valleys and the peaks of a twisted sheet do not fall on parallel lines. Observe that the sheet is parallel, and showing hydrogen bonds. Notice that in contrast to the hydrogen bonds of the antiparallel sheet shown above where the bonds were parallel here the bonds are diagonal to each other. Show psi and phi values for randomly chosen residues. There are a wide range of values for both psi and phi, +96 to +148 and -108 to -142, respectively. The above sheet shown in the context of domain 2 of glycogen phosphorylase. Examples of antiparallel sheets. Showing only the sheets, and with hydrogen bonds. <scene name='Sheets_in_Proteins/1dtg4/3'> Values of psi and phi for randomly chosen residues; these values range from +90 to +167 and from -98 to -178, respectively. These ranges overlap the values for the twisted parallel showing that there is no differences in the ranges for the two types of twisted sheets. Median values for psi and phi are +1400 and -1250, respectively.